Thread Protectors and their Use, Generally:
Where threaded tubular goods are manufactured and transported or stored prior to use, it is usual to provide protection for the treads which have been machined or formed at one or more ends of each tube. It is also typical that threaded tubulars are manufactured for later assembly into a multi-tube conduit, with each tube being joined to at least one other tube using the threads at the end of the tubes; this means that each tube typically will have a male (or “pin”) end with threads cut into the outside diametrical surface of the tube, and a female (or “box”) end with threads cut into the inside diametrical surface of the other end of the tube; a pin end being designed to threadably connect with a box end of another tube to form a string of tubulars. The box end may be comprised of a fitting of larger outside diameter than the tubular in order to accommodate internal threads with adequate inside diameter to receive matable pin-end threads of another tubular. It can be seen that with two types of threaded end to protect, there are logically two types of thread protectors required.
Threaded protectors are therefore typically either themselves formed to protect the pin-end or the box-end of threaded tubulars, and will thus either be male-thread protectors (protecting the pin-end threads) made to threadably fit onto and over the pin-end threads; or female-thread protectors (protecting the box-end threads) made to threadably fit into and cover the box-end threads.
Male-thread protectors are typically shaped as a cylinder with its internal side-wall machined or formed with threads to attach itself to a pin-end thread on a tubular. The protector may be closed at one end, like a can, or can be open at both ends.
Female-thread protectors are typically shaped roughly as a cylinder, with its external side-wall surface machined or formed with threads to attach itself into the box-end thread of a tubular. The protector may be closed at one or both ends, but is typically open at least at its outer end (when threaded into the box-end thread of the tubular).
When threaded tubulars are manufactured, it is usual for the threaded ends to be protected by installation of thread protectors as described above to be fitted, especially when the tubulars are to be stored or transported prior to use. When the tubulars are ready to be deployed or installed or used in the field (such as to form wellbore casing or drillstem, for example), the thread protectors must be removed before the tubulars can be attached one to the other to form their designed conduit or tubing string. This has typically been done manually by having an operator grasp the protector and turn it by hand until it decouples from the tubular. This process requires repetitive manual motion through a number of rotations of the protector, which promotes repetitive stress injuries and takes time (in the order of 60+ seconds per protector). In a typical well, several hundred tubulars may need to be prepared and connected to form a desired casing or tubing string, and the requirement may need to be met in a short period of time to reduce costs of idled rig equipment.
In the prior art, U.S. Pat. No. 4,442,737 (Miner) identified a potential solution to the issues raised above, and attempts to provide a mechanism for using externally provided rotational forces (such as provided by a hammer-drill or powered torque wrench) to spin thread protectors off (or onto) threaded tubular goods. Miner provides for a thread protector wrench for frictionally pneumatically engaging and removing thread protectors from tubulars; there are two styles of wrench disclosed, both operating on similar principles: a flexible material is deployed adjacent the outer diameter surface of a thread protector (being the surface away from the threads on the tubular onto which the protector is attached), and injecting fluid pressure into the tool to expand the flexible material, forcing it to engage frictionally with the surface of the thread protector; and then rotating the tool and flexible material in order to rotate the thread protector to remove (or replace) it from (or to) the tubular's threads. The Miner tool requires a source of pressurized fluid, fluid flow control means, a means of attaching the pressure source during activation of the engagement function and detaching the pressure source when it is desirable to rotate the tool, as well as inordinate stresses focused on the attachment point of the flexible bladder to the tool's rotation attachment to the external rotation/torque applicator.
It is, therefore, desirable to provide a system and apparatus for overcoming the obstacles in the prior art, reducing materials costs, time to build and associated time-dependent costs, and increasing useable lot space for medium to large-scale construction projects involving excavation and provision of useable basement structures which may also form foundations for the upper building structure.